The current paper presents the results of an investigation carried out across 20+ country-regions under the auspices of ICMI Study 15 into the structures, approaches and general characteristics of the mathematics preparation and development of teachers. The paper provides an analytic perspective on (a) teacher education systems’ characteristics including institutional arrangements and regulations; (b) teacher’s recruitment, selection, and credentials; (c) teacher education programs’ structure and approaches; (d) teacher educators’ characteristics; and (e) the structure and content of the curriculum.